With the popularity of smart terminals, demands on wireless data service experiences an explosive increase. As predicted, from 2010 to 2015, global mobile data traffic experiences a 24-fold increase, during 10 years from 2010 to 2020, the traffic will see a 500-fold increase. This is a great challenge for the service providing capabilities of the operators. Generally, mobile services of cellular networks are obviously inhomogeneous. According to statistics, about 60% of voice services and 90% of data services are provided indoors. Therefore, for the operators, providing good indoor coverage is an important means to keep customer retention and improve enterprise benefits. However, according to a survey, about 45% of families and 30% of enterprises confront the problem of poor indoor coverage. This is because the current means of providing indoor coverage are mostly based on outdoor macro-cell base stations. On this context, the concept of small base station is proposed in the industry as an effective means for solving the above problem. The small base stations refer to various low-power, small-coverage and flexibly-deployed wireless access points, and may become a development trend of the future base stations. With such small base stations, indoor coverage, hot spot coverage and deep coverage and the like issues of the mobile communication network may be addressed via mass deployment. This compromises defects of the macro cellular network, improves spectrum efficiency, improves network capacity, better accommodates development needs of the future mobile communication services, and improves user experience.
However, in practical deployment of the small base station, there are still many problems to be solved. Among these problems, interference is prominent. 3GPP LTE proposes the concept of full-frequency multiplexing to further improve spectrum utilization rate, that is, co-frequency networking is employed between different cellular networks. As a result, users at the edge of the cell are subject to severe co-channel interference, and the quality of service (QoS) thereof is degraded. With the deployment of small base stations, in a heterogeneous network constituted by small base stations and traditional macro base stations, the problem of co-channel interference becomes particularly prominent. Especially in indoor deployment of the small base station, mutual interference with the existing indoor coverage system is most likely caused, for example, in a DAS (a simple delay of the traditional macro base station may solve the problem of signal coverage, but system capacity cannot be improved), and thus practical application and deployment of small base stations are restricted.
In 3GPP LTE, an interference coordination mechanism based on collaboration between cells is proposed to reduce co-channel interference between cells, for example, ICIC, eICIC and FeICIC. The basic concept is to enable signals from adjacent cells are orthogonal to each other in the time domain, the frequency domain or the space domain, so as to avoid mutual interference. Nevertheless, implementation of the above interference coordination mechanism consumes some capacity. However, when the small base station and the DAS are in a hybrid deployment, it is hard for the interference coordination mechanism implemented between macro base stations, or indoor macro base stations and small base stations to given a full play. Therefore, a corresponding collaboration mode needs to be designed according to the characteristics such as indoor deployment and distributed deployment of the DAS, and a signal processing method needs to be introduced to suppress the interference.